Common practice is to use Role based access controls for Projects in tableau sites. For granular level you can apply it on workbooks. You can also use Active directory or other directory services as your directory. Take a look at this http://www.theinformationlab.co.uk/2014/06/11/understanding-tableau-server-permissions/
Dont forget to read the Tableau security guide (v8) https://www.tableau.com/sites/default/files/media/tableau_server_security_8.pdf
Let us know if you have any specific questions.